FOR L&T, A WORLD RECORD. FOR THE CLIENT, QUICKER PROGRESS.

Monopile technology

Constantly seeking new technologies to speed up construction, the team opted for monopile construction for the bridge pillars that has thus far been used successfully only in Scotland & South Korea. Deployed in India for the first time, with raw material sourced from Europe, the monopiles are environmentally friendly, significantly reduces work, time, and cost and is aesthetically more attractive. “By adopting monopiles that are in a range of 2.5 – 3.2 m in dia, we have reduced the number of piles from 704 to just 176,” flags off Raj. “This also means that we are putting up less piles on the seabed and thus disrupting the marine life less to that extent.”

The pandemic cleared the Mumbai roads for free movement

Considering the strategic importance of the project, MCGM was keen that construction was not disrupted by the pandemic so with special permissions, the project team continued work even during the lockdowns. “The lockdowns were a boon for us,” says Raj, with relief, gesturing towards the road outside the site that is choc-a-bloc with traffic in the early afternoon, that was previously considered a non-peak hour. “With the roads cleared of traffic, we could bring in material, move equipment and take away debris from the reclamation without any hinderances.” The Mavala TBM was delivered at site on 273 vehicles in quick time that would otherwise have taken months to transport on the normal Mumbai roads.

Gasping for oxygen

With oxygen supplies being diverted almost entirely for medical purposes to treat COVID patients, the team switched to plasma cutting that has now been adopted as a SOP even after oxygen supplies have been restored.

Accommodating workmen at site

With Mumbai reeling under the COVID scare, mobilizing workmen was an extremely difficult task and with so many restrictions on movement, transporting them was a nightmare. The team therefore developed a labour camp at site, equipped with all facilities, to address all these issues.

With 11 strategically placed cross passages for fast evacuation, the tunnels will be equipped with heat sensors, CCTV-based advanced traffic controls, Saccrado ventilation systems to pump in fresh air to main air parameters while work is in progress. The 2,072 rings in the tunnel consist of 16,576 precast concrete elements each weighing some 9 tonnes, equivalent to an
empty truck.

Once work started, the TBM smoothly burrowed its way to the end of the tunnel and then the team was faced with the arduous task of dismantling the TBM underground, lifting it part by part to the surface, transporting it to the new location where the second tunnel was to be launched, reassembling and lowering it to start boring. “All this would have taken several months and that is when our brainstorming gave us an absolutely out-of-this-world idea,” Sandeep pauses, perhaps thinking back to the moment when he had to take that call to go ahead with their plan. Their idea was to rotate the TBM in the tunnel itself and revise the TBM construction sequence. As per the earlier plan the 2^nd tunnel was to be constructed from Priyadarshini Park to Girgaon Chowpatty site like the 1^st drive which would have involved 6 months of work to dismantle the TBM, transport and re-assemble it at Priyadarshini Park. “We rotated the TBM inside the shaft and started the second tunnel from Girgaon Chowpatty within 3 months and saved us some 6 months of execution time in the process,” says an elated Sandeep. This will not only help in reducing the tunnelling activity but will also facilitate the other successive activities like MEP works to be started earlier.

“We are through with almost 75% of the tunneling and should be able to achieve breakthrough by December 2022,” says a confident sounding Pradeep Prasad, Construction Manager (Civil).

His colleague, Pradeep Kumar Sharma, Assistant Manager, P&M, Heavy Civil IC, reminds us that tunnelling is not only about TBM activity. “There is so much more to tunnelling including the MEP works, electricals, plumbing, ventilation, firefighting systems, live utilities and finally the road itself.” Both are unanimous that perhaps the most difficult aspect of MCRP is having to work and construct in the congested city of Mumbai. “In most places, we have very little space to maneuver,” laments Sharma, “Constructing on Marine Drive is particularly challenging, not just because of the density of traffic but being one of the city’s most important roads, very often our work is disrupted by VIP movement.
This stop-and‐start kind of work plays havoc with our delivery schedules and sometimes we have just 2–3-hour windows to work,” he points out with a long face.

Considering its sheer magnitude and complexity, MCRP is a dream project for any civil engineer, opines A H Khan,
Vice President & Head – Operations, Mumbai. “It involves tunnel cut and cover sections, huge reclamation, sea front protection with rocks of various sizes, underpasses, road works, large diameter monopiles, underground car park, viaducts with cast-in-situ, segmental launching involving girders and many more.” To execute such a massive project involving so many facets of construction, calls for deep understanding of all the deliverables, meticulous planning, and picture-perfect execution capabilities. “The teams at both packages have been constantly deliberating with project consultants, designers, and the Employer to improvise upon the deliverables, for them to be aesthetically pleasing and sustainable, with sharp emphasis on digitalization particularly BIM implementation, on-line monitoring of resources and data validation for operation excellence.”

November 2023 is fast approaching for Sandeep Singh and his hardy foot soldiers. They have already completed
a large section of the seawall, almost the entire reclamation and a fair number of the land piles, monopiles and superstructure jobs. There is still a mountain waiting to be climbed but the team is ready and raring to summit it.